Diffusion of dissolved carbonate in magmas: Experimental results and applications

Watson, E. Bruce; Sneeringer, Mark A.; Ross, Abigail M.

doi:10.1016/0012-821x(82)90065-6

Cited by 121 publications

(66 citation statements)

References 27 publications

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“…Sparks (1978), on the other hand, used the same data as input for calculations of the growth rates of H 2 0 vapor bubbles in ascending and erupting magmas. The same application was discussed less thoroughly by Watson et al (1982) with regard to their diffusivity information on dissolved carbonate. In addition, these latter authors noted that because dissolved H 2 0 and CO 2 diffusivities are quite different, the possibility of diffusional fractionation of the two gases during bubble growth (and during other diffusion-controlled processes) must be recognized.…”

Section: Magmajv Olatile Interactionsmentioning

confidence: 92%

“…Although the experiments on synthetic basalt covered a much smaller temperature interval (1350 to 1500°C), the Arrhenius parameters appeared to be similar to those ofthe simple aluminosilicate. Watson et al (1982) concluded on the basis of indirect reasoning that dissolved carbonate diffuses as ionic C0 3 2 -• Current work at Rensselaer includes re-examining "C02" diffusion in magmas with a view toward broadening the data base to other melt compositions and including the effect of concurrently dissolved H 2 0. It is already clear that water has a pronounced effect on CO 2 diffusion, causing increases in Dcarbonate similar to those documented for other elements (i.e., orders of magnitude at crustal melting temperatures).…”

Section: Crystal Dissolutionmentioning

confidence: 99%

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Chemical Diffusion in Magmas: An Overview of Experimental Results and Geochemical Applications

Watson¹,

Baker²

1991

Advances in Physical Geochemistry

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The subject of chemical diffusion in magmas has attracted the interest of petrologists and geochemists seeking to place time constraints on phenomena ranging from magma mixing to crystal growth. Experiments have been devised to examine chemical diffusion effects during such processes as interdiffusion of two liquids, growth and dissolution of crystals, exchange of halogens with oxygen in the air, reduction or oxidation of dissolved iron oxide, and introduction of dissolved volatiles. A few experiments have even been done using a temperature gradient to induce thermal migration.Many of the studies carried out to date have incorporated variations in temperature, pressure, and dissolved H 2 0 content, so the collective results allow diffusivities in magmas to be estimated quite well for most geologicallyrealizable conditions. In general, the following major characteristics appear to hold:(1) Network-forming species, most notably Si0 2 , are the slowest-moving magmatic components, although network-modifiers that form stable complexes in the melt may be equally sluggish; (2) alkalies, divalent cations, oxygen, and fluorine are the most mobile magmatic components when their transport is not rate-limited by counterdiffusion of slower species; and (3) the effect of H 2 0 content on chemical diffusion of most components (including H 2 0 itself) is extremely large, sometimes amounting to several orders of magnitude at crustal melting conditions.

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Section: Magmajv Olatile Interactionsmentioning

confidence: 92%

Section: Crystal Dissolutionmentioning

confidence: 99%

Chemical Diffusion in Magmas: An Overview of Experimental Results and Geochemical Applications

Watson¹,

Baker²

1991

Advances in Physical Geochemistry

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“…Also in Fig. 18 are C tracer diffusion high viscosities) the diffusivities of some cations data of Watson et al (1982) for synthetic Na 2 Oare so much faster than oxygen that the network Al 2 O3-SiO 2 and basaltic melts. The C data coincide oxygens appear in fixed structural sites during a with the slower group of Henderson et al (1985).…”

Section: Logio Units) Ions During Such Exchanges the Bonds To Cationsmentioning

confidence: 96%

Relaxation in silicate melts

Dingwell¹,

Webb²

1990

ejm

420

253

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Abstract:The glass transition is a kinetic barrier that divides the behavior of silicate melts into two types, liquid and glassy. Liquid behavior is the equilibrium response of a melt to an applied perturbation, resulting in the determination of an equilibrium liquid property. The equilibrium may be stable (superliquidus) or metastable (subliquidus). Glassy behavior occurs when the timescale of the perturbation is too short for melt equilibration. This can occur when the frequency of an applied sinusoidal perturbation is too high or when the observation time of an experiment is too short. The time-or frequency-dependent response of the structure and properties of a melt to a perturbation is termed relaxation. Liquid and glassy behavior are relaxed and unrelaxed behavior, respectively.Linear viscoelastic theory provides mechanical models for the prediction of the isothermal transition from liquid to glassy behavior. A simple series combination of Hookean spring and Newtonian dashpot (a Maxwell element) is capable of predicting the timescale corresponding to the glass transition from the ratio of the relaxed viscosity to the infinite frequency elastic modulus. We review some experimental work on silicate melts that can be used to constrain the location of the glass transition in time-temperature space at 1 atm pressure (e.g., ultrasonic wave propagation, fiber elongation, torsional testing, scanning calorimetry).The microscopic origin of the glass transition in silicate melts is related to the exchange ofSi-O bonds. Recent" Si NMR work indicates that the Si-O bond exchange frequency matches the timescale of the glass transition. This explains the Newtonian viscosity of silicate liquids. No extended species (e.g., "polymers") can exist at higher temperatures and longer timescales than the lifetime of the fundamental Si-O bond. Silicate melts, however, become non-Newtonian as the strain rate approaches the equilibration rate of the Si-O bonds. Such a correlation between Si-O bond exchange and the viscous flow mechanism, in turn, explains the success of the Eyring relationship in relating high temperature oxygen and silicon self-diffusion to viscosity.Knowledge of the structural relaxation timescale is important in extracting equilibrium information from studies of the structure and properties of quenched glasses. Quench rate-dependent speciation data for glasses imply a temperature-dependence of the species equilibrium in the liquid state. Estimation of the relaxation times associated with the quench rates allows reconstruction of the temperature-dependence of homogeneous equilibria in liquids.Experimental work on silicate melts should consider the location of the experimental method in time-temperature space, with respect to the glass transition. Diffusivity measurements, for example, are influenced by the glass transition. When the duration of a diffusivity experiment crosses the volume relaxation time, an inflection in the temperature-dependence of diffusivity of cations is observed. A second "transition" in diff...

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“…2. Cationic tracer diffusivity data (Watson et al, 1982;Henderson et al, 1985) vs. melt viscosity (calculated using the method of Shaw, 1972). The diffusivity of oxygen is calculated from the Eyring relation.…”

Section: Observation Time-scale (%)mentioning

confidence: 99%

“…Also included in Fig. 2 are the C tracer diffusion data of Watson et al (1982) for synthetic Na20-A12Oa-SiO2 and basaltic melt. The C data coincide with the slower group of Henderson et al (1985).…”

Section: Observation Time-scale (%)mentioning

confidence: 99%

Effects of structural relaxation on cationic tracer diffusion in silicate melts

Dingwell

1990

Chemical Geology

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Dingwell, D.B., 1990. Effects of structural relaxation on cationic tracer diffusion in silicate melts. Chem. Geol., 82:209-216.The glass transition in silicate melts is a curve in time-temperature space marking the transition of the melt structure from an unrelaxed, disequilibrium glass to a relaxed, equilibrium liquid. Tracer diffusivity data obtained in glasses vs. liquids cannot be compared without consideration of the effects of this transition. For tracer diffusivity experiments, two time scales are important, the time duration of the experiment (~d) and the inverse of the jump frequency (vp) of the tracer.When the time duration of the experiments reaches the relaxation time-scale (~d = rs) of the melt a transition occurs from diffusion in an unrelaxed matrix (undergoing vibrational thermal expansion) to diffusion in a relaxed matrix (undergoing equilibrium, configurational and elastic, thermal expansion). At this transition, an inflection is observed in the temperature dependence of cationic tracer diffusivity. At temperatures below the inflection, the diffusivity is Arrhenian whereas at temperatures above the diffusivity is non-Arrhenian.At high temperatures the tracer diffusivities of the cations approach the value of diffusivity obtained from the Eyring relation ( rp = ~s). The contrasting, high-temperature, composition dependence of Na and Li vs. Co, Cs, Sr, Ba, Eu, Fe and C diffusivities can be explained in terms of the Eyring (network 0 and Si) diffusivity influencing the latter group. The contrasting high-vs. low-temperature, composition dependence of Ba and Sr diffusivities can be similarly explained. These latter observations indicate that all cationic diffusivities will be within a loglo unit of the Eyring oxygen diffusivity in melts with viscosities below 10 P.

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Diffusion of dissolved carbonate in magmas: Experimental results and applications

Cited by 121 publications

References 27 publications

Chemical Diffusion in Magmas: An Overview of Experimental Results and Geochemical Applications

Chemical Diffusion in Magmas: An Overview of Experimental Results and Geochemical Applications

Relaxation in silicate melts

Effects of structural relaxation on cationic tracer diffusion in silicate melts

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